How can i render the reflections i see in the Look Dev viewport in Blender 2.8
You would need to apply the same HDRI to your world as background. The scene lights in Look Dev are only meant to give you a good preview and not an actual representation of the lighting in your scene. If you want to use the exact same file, you can find it in your Blender installation under 2.80\datafiles\studiolights\world\forest.exr. Otherwise I'd recommend HDRIs from hdrihaven and/or setup a three-point lighting using Blender's lights (Add > Light).

The image below shows how to setup a background texture for your world.